Legg-Calve-Perthes disease following transient synovitis. How often?

Forty-one children with transient synovitis of the hip and 10 children with Legg-Calve-Perthes disease were followed. All 41 cases of transient synovitis had a benign outcome. In this series, nine of the 10 children with Legg-Calve-Perthes disease were diagnosed upon their first roentgenographic examination. One child whose first diagnosis was transient synovitis remained symptomatic for 4 months, when he developed roentgenologic changes consistent with Perthes disease. The literature is reviewed and 455 cases of transient synovitis analyzed. Only one patient with transient synovitis developed Legg-Calve-Perthes disease after having been asymptomatic for a period of 3 months. In 17 other cases, symptoms persisted until Legg-Calve-Perthes was diagnosed. It is suggested that transient synovitis is a benign disease and that only children with protracted symptoms are at risk to develop Perthes disease.